1. Field of the Invention
This invention relates to a multiple element fuse and in particular a multiple element fuse of open construction wherein each fusible element is mounted within an insulative tube.
2. DESCRIPTION OF THE PRIOR ART
Prior art multiple element fuses often include a plurality of fusible elements each mounted within an insulative tube. Fusible elements mounted in this fashion are commonly referred to as "tube fuses". Such multiple element fuses conventionally have end bells soldered at opposite ends of the tube fuses, the tube fuses being exposed therebetween. Devices of this type are designed to operate near their current carrying capacity, and require an open construction to allow greater air cooling of the individual tube fuses. It is frequently desirable to provide air flow through the interior of the fuse, or to otherwise provide a forced cooling of the tube fuses with a fluid medium.
A blade terminal typically is formed with or joined to the end bells of the multiple element fuses for connection with bolts or similar fasteners to elongated busbars of electrical equipment. Frequently, the busbars are not spaced apart to the exact distance required to achieve alignment with mounting holes located in the blade terminals of the multiple element fuses. As such, one or both of the busbars must be deflected to provide alignment with the blade terminals, to allow a bolted connection to be made therebetween. This frequently imposes tensile forces on the multiple element fuse end bells. As such, when the fuse operates to clear an electrical overload, the soldered connection between the end bells and the tube fuses sometimes weakens or melts sufficiently to allow the busbars to resume their rest position, thus pulling the fuse apart, causing the individual tube fuses to fall away possibly into the switch gear within which the fuse is installed.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a new and improved multiple element fuse comprising a plurality of tube fuses joined at the ends thereof to end bells designed for connection to spaced busbars, which fuse remains mechanically intact subsequent to the operation of the fuse to clear an electrical overload despite the application of tensile forces applied to the end bells thereof.
It is another object of this invention to provide a multiple element fuse of the above-described type which is relatively inexpensive to fabricate, simple in design yet is effective in use.
The foregoing objects are accomplished in accordance with the present invention, in one form thereof, by providing a multiple element fuse comprising spaced apart end bells having blade-like terminals for connection to busbars of an external electrical circuit. A plurality of tube fuses are soldered at opposite ends to the metallic end bells, respectively, to provide mechanical and electrical connection between the fuses and end bells. Fasteners having the general dimensions of the tube fuses, but including a ceramic insulating body are also mounted between the end bells. Connectors, such as, for example, rivets, threaded studs, or the like formed on ferrules at opposite ends of the fasteners, are employed to mechanically couple the fasteners to the end bells. Such fasteners preserve the spacing between the end bells even when the fuse is subjected to tensile forces. The use of a hollow ceramic body and hollow connectors at the ends of the fasteners permits the passage of coolant through the fasteners for cooling the multiple element fuse, if desired.